It is difficult because it belongs to the subject of applied mathematics after all, and mathematics is nothing simple, right? From the perspective of curriculum, basic courses are several points and generations, which is different from most science and engineering (high mathematics and high line generation). Moreover, in many statistics, functions and stochastic processes are both basic disciplines, which are difficult in themselves.

It's relatively easy: in mathematics, statistics are widely used, and you need to master certain computer skills (C++, database, etc. ) In practice, statistical software (SPSS, R, SAS) is mainly used. So, in fact, you don't need to fully understand its principle, as long as you fully master the use of the software, you can carry out basic statistical analysis. To put it bluntly, sometimes you don't need to know "why", you just need to know "how". Relatively speaking, the other part-pure mathematics has not "how to do it", but has been studying "why", which is a highly abstract subject. So statistics, as a branch of applied mathematics, is definitely simpler than pure mathematics. (If the goal is to pass the exam, there is no difficulty ...)